Well perforating apparatus



Nov. 22, 1960 F. H. BELL WELL PERPORATING APPARATUS Filed April s, 19572 Sheets-Sheet 1 lNvENToR Frederick H. Bell BY 'M ATTORNEY Nov. 22,19h() F. H. BELL WELL PERFORMING APPARATUS 2 Sheets-Sheet 2 'Filed April3, 1957` INVENTOR Frederick H. Bell BY (Q ATTORNEY United States PatentC WELL PERFoRATING APPARATUS Frederick H. Bell, Arlington, Tex.,assigner to Jet Research Center, Inc., Arlington, Tex., a corporation ofTexas Fixed Apr. s, 1957, ser. No. 650,335

7 claims. (ci. 1oz- 20) This invention relates to well perforatingapparatus and more particularly to such apparatus in which individualshaped explosive charge units are linked toygether to form a chain ofunits. The invention also relates to the individualV shaped chargeexplosive units themselves.

In the perforation of oil wells, it is desirable to have perforatingapparatus that may be quickly assembled in the eld to provide aperforating gun of a length and having a number of perforating unitssuited to the job at hand. For the sake of simplicity and speed ofoperation, it is also desirable that a minimum number of tools be neededto assemble the perforating apparatus.

Frequently, oil wells are completed by so-called permanent typecompletion methods. In these methods, tubing is set in the casing andthe top of the casing is capped with the usual well head equipment priorto performance of the perforating step. Perforating apparatus is thenlowered by cable through the tubing and out of its lower end to thelevel at which the casing is to be perforated and the apparatus isfired. Any parts of the perforating apparatus that remain attached tothe cable after firing are retrieved by withdrawal through the tubing.For these purposes, the perforating apparatus must be as efficient aspossible. One requirement is that the apparatus must have a closesliding fit in the tubing in order to accommodate the largest possiblequantity of explosive in each perforating unit which is designed to firegenerally laterally of the well bore. At the same time, the apparatusmust not bind in the tubing during descent.

The permanent type completion method is being adapted to directionalwells wherein the well may be drilled vertically for a certain distancedown from the earths surface, and thereafter drilled at an angle to thevertical. Also, in some offshore installations the production tubing mayrise vertically from the bottom of the well and thereafter be turnedlandward and run to the shore. In either case, the tubing is rathersharply bent at certain points which makes it very diicult to runperforating apparatus through the tubing.

An object of the invention is to provide a well perforating apparatuswhich may be quickly assembled in the iield principally from a pluralityof identical, shaped explosive charge units. Due to the specialconstruction of the charge units, such assembly may be accomplishedwithout the use of tools.

Another object is to provide a perforating unit, a plurality of whichmay be linked together to form a perforating assembly of any desiredlength.

Another object of the invention is to provide a perforating assemblyhaving articulated joints and being adapted to pass through relativelysharp bends in small dented or otherwise damaged to a limited degree, asby, being burred or somewhat corroded in the bore. Still another objectis to provide apparatus for perfo@V rating oil, gas and water wells thatmay be employed in permanent type completion methods. Yet another objectof the invention is to provide wellV perforating apparatus that isrelatively simple and inexpensive to manufacture and that may beconveniently and rapidly assembled in the eld. Y Another object of theinvention is to provide a well perforating apparatus including aplurality of capsulated shaped explosive charge perforating units linkedtogether by a pivotal linkage construction having cooperating stops forlimiting relative pivotal movement ofv adjacent units. Another object ofthe invention is to provide blank interval members in a well perforatingapparatus of the character disclosed which members carry no perforatingcharges but are linked in the assembly like theperforating unitsthemselves.

These and other objects and -advantages of the inven l tion as mayappear hereinafter are achieved in a well perforating apparatus that isadapted to Vbe passed through small diameter tubing having relativelysharp bends which includes a plurality of longitudinally aligned wellperforating units, articulated means linking adjacent units together toform a chain, and means limiting the angular movement of adjacentperforaiting units about the included linking means. The articulatedjoints lend flexibility to the chain of units permitting it to passthrough sharply curved sections of narrow tubing. The articulated jointsmay include a pivot pin carried by one unit received in a complementaryhole provided in an adjacent unit. Such joints may include a key or thelike that retains the pivot pin in the hole and comple mentary stopmeans on adjacent units limiting their relative' angular movement aboutthe pivot point. More particularly, the shaped explosive charge wellperforating apparatus of the invention has a plurality of verticallyaligned well perforating units, each unit including a pressureresistant, frangible container having a shaped explosive charge thereinadapted upon detonation toV project an explosive jet outwardly through awall of the container and having a vertical axis' intersecting the axisof the explosive jet at a substantial angle, the vertical axes of theunit being in alignment to define the vertical axis of the wellperforating apparatus; the container of each unit having an upstandingand a'depending arm; one of said arms having a terminal planar facecontaining the vertical axis of the unit; a cylindrical pin carried bysaid one arm, the pin extending'from the terminal face and having itsaxis intersecting the vertical axis of the unit at right angles, the pinproviding a trans verse keyhole therethrough spaced from the terminalface, and a lug extending radially from the pin between the terminalface and the keyhole. The other of the arms has a Iterminal planar facecontaining thevertical axis of the unit, the other arm providing acylindrical hole therethrough having its axis intersecting the verticalaxis of the unit at right angles within the terminal planar face, theother arm having a lug-receiving recess communicating with the ho-le andextending radially' outwards therefrom. The perforating unitsV arelinked to gether to form a chain wherein the pin on the onearm of oneunit is received in the hole of the other armof an adjacent unit, theterminal faces of the arms are'in abutment and the lug is received inthe recess, the sides of the lug being spaced from the sides of therecess to limit arcuate movement of the pin in the hole, and a `key isdisposed in the keyhole of the pin to retainthe arm of the adjacent unitin the pin.

The present inventionis an'improvement inthe in# Patented Nov. 22, 1960vention disclosed and generically claimed in the copending applicationof Blake M. Caldwell, Serial No. 650,334, led April 3, 1957, for WellPerforating Apparatus, which copending application is assigned to thesame assignee as the present application.

The invention will be described with greater particularity withreference to the drawings in which:

` Fig. 1 is a vertical sectional view through a portion of an oil wellshowing an exemplary embodiment of the weli perfor/ating apparatus ofthe invention suspended in the well;

Fig. 2 isv an enlarged elevational View of one of the shaped chargeperforating units used in the apparatus of Fig. 1;

i Fig. 3 is a right hand side view of the shaped charge perforat'ingfunit of Fig. 2, parts of -the shaped charge container being broken away;

` Fig. 4 isa plan view thereof;

Fig. 5 is a bottom view thereof;

Fig. 6 is a still further enlarged fragmentary view showing one of thearticulated joints of the well perforating apparatus;

Fig. 7`is a left hand view of the joint shown in Fig. 6;

Fig. 8 is an elevational view of aV blank interval unit; and

""Fig. 9 is a left hand view of the blank interval unit shown in Fig.V8.

-Referring to the drawing, particularly to Fig. 1, there is shown asection of an oil well having a casing 10 in which production tubing 11is set. The perforating apparatus of the invention is shown as beingsuspended from lthe cable 12 which carries, as is conventional, aconductive wire through which current is passed for the purpose of ringthe well perforating apparatus. The well perforating apparatus islowered from the surface of the earth in well known manner.

' The cable head 13 hangs from the lower end of the cable. From thebottom of the cable head an arm 14 depends, and this arm supports aplurality of interlinked,

shaped explosive charge, well perforating units desig-` nated by thegeneral reference numeral 15. The perforating units are red in a mannerto be explained more fully hereinafter by a detonating fuse or Primacord16 disposed adjacent the rear ends of the shaped charge units. Aixedrtothe lower end of the Primacord 16 in detonating relation thereto is adetonator or blasting cap 17.A A pair of wiresv18, through whichigniting current is conducted to the blasting cap 17, extend fromtheblasting cap and are wound in an upward direction about the chainofperforating units to enter the cable head 13 in which they are connectedto the tiring circuit.

.The perforating apparatus is seen partially inside of the lower end ofthe tubing 11. Before, firing itis lowered below the bottom of thetubing to a point opposite the section ofthe casing to be perforated.

Referring to Figs. 2 through 5, the perforating unit ofthe invention hasa charge case 19 closed at its rear end by a cap 20. The cap fitstightly in the rear end ofthe case and the case may be sealed againstingress of bore fluids by means of an O-ring 20a or similar compressibleseal interposed between the cap and the case. Disposed within the casenear the rear end thereof is a charge of compressed high explosive 21having a forwardly facing cavity therein lined with an inert liner 22,preferably of copper or other metal. Stand-01Tr space is providedbetween the front face of the liner 22 and the front wall 23 of thecharge case to permit the perforating jet to form Within the case upondetonation of the charge. Y

The cap 20 has a rearwardly projecting cylindrical boss 24 through whichis bored a vertically extending fuse passage 2,5. As `shown in Fig. 5,the cap 20` hasa .booster cayity 26 separated from the fuse,passage.25by a thin wall 27' through which detonating energy fronjrtheP rimj asord, Strang-nite@ to; a,-.b 19Ste -har.ge die cavity- Thebooster charge initiates the main explosive charge 21 to produce anexplosive jet from the liner, the jet being projected forwardly alongthe cylindrical axis of the charge. This jet forms in the air spaceforwardly of the liner 22 and penetrates the front wall 23 of the chargecase. Thereafter it penetrates the wall of the adjacent casing andperforates the surrounding earth formation. Upon detonation, some of theenergy of the explosive charge serves to break or fracture the chargecase and arms, formingl small fragments and particles that fallharmlessly to the bottom of the Well.

The charge case has an upstandng arm 27, the face 28 of which containsthe vertical center line CL of the unit. The face 28 is disposed atright angles yto the charge axis. From the upper terminal end of theface 28 a cylindrical pivot pin 29 extends perpendicularly, the axis ofthe pin intersecting the center line. A lug 30 projects radially frornkthe side of the pin 29 and, extends in aY direction upwardly alongy thecenter line CL. The lugY also extends axially along the side, of the pin29 to a point near theY hole. or keyway 50 and between the hole 50 andthe arrn f ace 28; A key 51 is inserted through the hole 50 in linkingthe charge units together, asV will be explained more fully hereinafter.As shown, the. upstanding arm 27' is of yuniform thickness; however, thethickness does1 not, have to be uniform as long `asv the terminal end.of the planar face 2 8- adjacent the pin 29 is in a plane containinglthe center line.

The case. of*V the unit also has a depending arm 3'1 which, in theembodiment shown, is` of the same length as the upstanding arm 27'. Thesurface 32 of the depending arm contains the center line of theperforating unit. A cylindrical hole 3 3 isformed' in the lower endofthe depending arm.` This hole is` at right angles to` the plane ofVthe surface 32 and its axis intersects the center line. Extendingupwardly from the hole 33y is an arcuateslot 34 thatcommunicates thehole andj extends in a vertical' direction along the center line CLofthe perforating unit. The arcuate slot extendsentirely through thear1n351., Itv

receives the lug 3d of a subjace'nt perforating unit when the apparatusis assembled and' limits the pivotal movement ofl adjacent perforatinglunits. In, the particular form shown, the terminal end ofthe dependingarm is of uniformV thickness and the lower endof the 'facel 32j containsthe center linie. However, the end of the arm near the case mayV` bethicker or, thinner than shown as desired; It will b e noted; that thedepending arm makes an angle of 30"L with the axis ofthe shapedexplosive charge as bestrseen inl Fig. 5..

Figs. 6 and 7 show inv enlarged fragmentary detail the mannerin whichtheupstanling arm 27'ofone perforating unit is linkedtothefdepending`arm 31 of an immediately superjacent.shaped'charge unit. Itwill be seen,that the pin y29'is receivediin the lroler33` with the lug 30;disposedjin the arcuateslot 34.` A cotter key 531V is inserted in thekeyway Stl'ofthe pin29rand the ends of the cotter keyv are bentover asshown to secure the depending arm 31 of the upper perforating unit tothe pin 29. Asclearly shown in Fig. 6.,'l the lug Y1.20 is .narrowerthan the arcuate slot 3.4,so that a limitedpivoting of the arm 31 yonthe pin 29 is permittedjbefore the sides of the lug engage the sides ofthe arcuate slot to stop the pivotal movement in either direction. Inpractice, it has been found that a pivotal movement of from a fewdegrees to as much as 30 to 45 is desirable andthelug and arcuateslotmay be` proportionedtorpermit any desired pivotal movement. The diameterof theghole 33,-issomewhat greaterv than thediameterroffthe pin 29providing a loose-fit, ofy the pin in the hole. Itis also seenthat/ theradiusl of the lug 30 is. somewhat smallenl than; the Vvradius of thearcuate slot 34.whicha ls oprovid e s aloo se t Referring to Fig.- 7 itis seen@ that -the'distancebfronjr theA terminal vplanar -face 28Offfhezntrlfte the Cotter-.key 5ltis1s0mewhatf-greater tha 1111thCkneSs/Offfhe depending-anvil.. providing fcrratfreestOtrtlaefanallbetweensthe; cottenkeyf'and the a'rm A27. This free litallows limited rocking movement in the plane of the drawing of Fig. 7 ofthe arm 31 in relation to the arm 27 and thus enhances the flexibilityof the assembled perforating gun.

It will be apparent that the perforating units may be readily linkedtogether and unlinked without the use of any tools, it being merelynecessary to manually insert or remove the cotter key 51. As is seenfrom Fig. 7, the terminal planar face 32 of the arm 31 is opposed to theterminal planar face 28 of the arm 27 when the units are properlyassembled. Thus, the center lines of adjacent charge units aresubstantially in alignment.

The charge units in assembled relationship as shlown in Fig. l areadapted to be run through narrow tubing with close clearance. For thispurpose, the charge containers are especially dimensioned to providesurfaces that will slide through narrow tubing without binding and willmaintain alignment of the charge units. As seen in Figs. 3, 4 and 5, thefront face 23 of the charge case is a segment of -a sphere having itscenter on the center line of the charge unit at its intersection withthe horizontal axis of the charge case 19. The boss 24 has a sphericalrear face with its center at the same point and having the same radiusas the front face 23. The circular rear edge of the charge case 19 liesin this sphere as does also the circular forward edge of the charge caseWhere the spherical front face 23 intersects the cylindrical portion ofthe case 19. Thus it is seen that the charge case and cap provide acontainer in which all surfaces that can slide against the tubing arelocated on a spherical surface having its center on the center line ofthe perforating unit and preferably at a point midway between the axisof the pin 29 and the axis of the hole 33. Whereas, the arms 27 and 31are shown as being of equal length, it will be understood that they mayhave dilferent lengths, if desired, or they may be proportionatelylonger for shorter than shown in the drawings.

Owing to the hereinbefore described geometery of the charge unit, alinked assembly of such units will readily pass through a straightlength of tubing having a bore with a diameter only slightly larger thanthe diameter of the spherical surface containing the faces and edges ofthe charge container that make sliding contact with the bore of thetubing. These faces and edges are termed the skating faces of the chargecontainer, since they slide or skate along the bore of the tubing. Suchan assembly of units is free to rotate on lits vertical axis within theconfines of closely itting straight tubing without substantial lateraldisplacement of any of the units from alignment with the Vertical axisof the assembly and without becoming lodged in the tubing as it islowered therethrough. Moreover, the articulated joints linking adjacentunits together and the angular phasing of such joints about the verticalaxis of the assembly allow the assembly to pass readily through rathersharply curved lengths of closely fitting tubing.

The foregoing is exemplified in an actual embodiment of the inventionconstructed in accordance with the acoom-panving drawing in which thedistance between centers of the pin 29 and the hole 33 was 3, thediameter of the spherical surface containing the aforementioned facesand edges of the charge container was 11%6, and the center of thespherical surface was located on the center line of the charge unitmidway between the pin 29 and the hole 33. Ten charge units soconstructed and dimensioned when linked together to form a chain, asshown in Fig. l, were found to run freely in straight lengths of tubinghaving a bore measuring 2" in inside diameter and to negotiate bends insuch tubing having a radius of 5 withlout binding or becoming lodgedtherein.

In preparing or assembling a perforating gun in the field, a charge 15is linked to the arm 14 of the cable head 13. The arm 14 has a hole andarcuate slot there thro-ugh, similar to the hole and arcuate slot of thecharge unit hereinbefore described, in which the linking pin of thetopmost charge unit is inserted. As many additional perforating units asdesired are added to form a chain of units. It will be seen thatadjacent charge units are disposed at an angle of to each other aboutthe vertical axis of the assembly. Detonating fuse 16 is threadedthrough the passageways 25 of the perforating units and wound about theassembly in helical disposition as shown. The lower end of the fuse 16is equipped With a detonator 17, the wires 18 of which are led upwardlyto the cable head in which they are connected to the firing circuitwhereby the detonator may be initiated from the surface of the earth.The assembly is lowered into the well as shown in Fig. l to the desiredlevel. The tiring circuit is energized. The blasting cap 17 detonatesthe Primacord 16 which practically simultaneously detonates theindividual perforating units 15 to perforate the casing and surroundingearth formation. The charge units 15 are frangible and are broken intosmall fragments which fall to the bottom of the well as innocuousdebris. The cable head 13 is of massive construction and is notdestroyed by the explosion. It is withdrawn after tiring for re-use.

While the well perforating unit shown in the drawings has but a singlehole 33 in the depending arm 31, it is contemplated that an additionalhole or holes of the same kind may be formed in the arm 31, thus givinga selection of holes in any one of which the pin of an adjacent unit maybe inserted, whereby the spacing of the charges may be varied inassembling the units. The plurality of holes are spaced along the centerline of the charge unit. Score marks may be made between adjacent holesalong which that portion of the arm 31 below the hole that is Vselectedfor use may be broken olf and discarded.

A blank interval member or unit 52 is shown in Figs. 8 and 9. This unithas an elongated flat body 53 having a pin 29' at the upper end providedwith a keyway 50' and a lug 30' similar to the pin and lug constructiono-f the perforating unit shown in Figs. 2 through 5. The axis of the pin29 intersects the center line at right angles as best seen in Fig. 9. Atthe lower end of the blank interval unit is provided a liange 54 thatlies in a plane at right angles to the plane of the body 53. The surface55 of the flange includes the center line CL. A cylindrical hole 33 isformed through the flange 54 and a connected -arcuate lug receiving slot34' is also provided for purposes similar to the hole 33 and arcuateslot 34 in the depending arm 31 ofthe shaped charge unit shown in Figs.2 through 5. Although the flange 54 of the illustrative blank intervalunit is shown as being at right angles to the plane of the body 53 andparallel to the axis of pin 29', it will be understood that this anglemay be varied as desired.

It will be apparent that one or any number of the blank interval membersmay be inserted in or substituted for the shaped charge explosive units15 in the assembly shownin Fig. lV where it is desired to space theactive charge units 15 at desired vertical intervals.

From the foregoing description of -a typical embodiment of theinvention, persons skilled in the art will readily perceive a widevariety of variations and modifications coming within the spirit of theinvention and the scope of the claims. For example, it is contemplatedthat the detonating fuse 16 may be tired from the top instead of fromthe bottom by merely changing the position of the blasting cap 17. it isalso contemplated that the lower end of the assembly may be providedwith a suitable bull plug if desired. lt is also contemplated that theperforating units need not embody shaped explosive charge devices;instead, they may include bullet perforating devices. Although, in theillustrative chain of units herein disclosed, adjacent charges arephased at angles of 120 to each other, any other convenient phase anglemay be employed; for example angles of 60, 90 or 180 may be foundconvenient, or all charges may face in the same direction.

I claim:

1. Shaped explosive charge well perforating apparatus adapted to bepassed through small diameter tubing having relatively sharp bendscomprising: a plurality of vertically aligned well perforating units,each unit including a pressure resistant, frangible container having ashaped explosive charge therein adapted upon detonation to project anexplosive jet outwardly through a wall of the container and having avertical axis intersecting the axis of the explosive jet at asubstantial angle, the vertical axes of said units being in alignment todefine the vertical axis of the well perforating apparatus; thecontainer of each unit having a single upstanding and a single dependingarm; one of said arms having a terminal planar face containing thevertical axis of said unit; a cylindrical pin carried by said one arm,said pin extending perpendicularly from said terminal face and havingits axisv intersecting the vertical axis of said unit, said pinproviding a transverse keyhole therethrough spaced from said terminalface, and a lug extending radially from said pin between said terminalface and said keyhole; the other of said arms having a terminal planarface containing the vertical axis of said units, said other armproviding a cylindrical hole therethrough extending perpendicularly tothe terminal planar face and having its axis intersecting the verticalaxis of said unit, said other arm having a lug-receiving recesscommunicating with said hole and extending radially outwards therefrom;said perforating units being linked together to form -a chain whereinthe pin on the one arm 4of one of said units is receivedv in the hole ofthe other arm of an adjacent unit, the terminal faces of said arms arein abutment, and said lug is received in said recess, the sides of saidlug being spaced from the sides of said recess to limit arcuate movementof said pin in said hole; and a key disposed in the keyhole of the pinof said one arm retaining the arm of the adjacent unit on the pin.

. 2. Well perforating apparatus adapted to be passed through smalldiameter tubing having relatively sharp bends comprising: a plurality ofvertically aligned well perforating units; each unit having a -singleupstanding and a single depending arm; each of said arms having aterminal planar face, said terminal planar faces containing at least onecommon straight line; said units being assembled with the terminalplanar face of the depending arm of each unit abutting the terminalplanar face of the upstanding arm of the immediately subjacent unit;pivot means interconnecting adjacent units for relative pivotal movementof said adjacent units about an axis'extending perpendicularly from saidabutting planar faces and intersecting said common straight line;complementary pivot interlocking ymeans carried by said arms; andcomplementary stop means carried by said arms limiting relative pivotalmovement of the units about the axis of said pivot means.

3. Well perforating apparatus as defined in claim 2 wherein said pivotmeans includes a pin extending fromone of said abutting planar facesreceived in a complementary hole extending from the other of saidabutting planar faces.

4. Well perforating apparatus as defined in claim 2 tending radiallyfrom said hole.

5. Well perforating apparatus as defined in lclaim 2 wherein said pivotmeans includes a pin extending from one of said abutting planar facesreceived in a hole extending from the other of said abutting planarfaces, said complementary stop means includes a lug extending radiallyfrom said pin received in an arcuate slot extending radially from saidhole, and means preventing withdrawal of said pin from said hole.

6. A well perforating unit comprising: a container having an explosivecharge therein adapted to project a perforating means outwardlytherefrom; a single upstanding unit-interconnecting arm on saidcontainer; a single down- Wardly extending unit-interconnecting arm onsaid container; each of said arms having a terminal planar face; saidterminal planar faces containing at least one common straight line;complementary pivot means carried by said arms and extendingperpendieularly one from each of said terminal faces with the pivot axesof said pivo-t means intersecting said common straight line;complementary pivot interlocking means carried by said arms; andcomplementary pivotal-movement-limiting stop means carried by said arms.

7. A well perforating unit as dened in claim 6 wherein saidcomplementary pivot means includes a pin extending from one of saidterminal faces and a hole extending from the other of said terminalfaces; and wherein said complementary pivotal-movement-limiting stopmeans includes a lug extending radially from said pin and an arcuateslot extending radially from said hole, said slot having a greaterradius and a greater arcuate length than said flug, said lug and saidslot each being spaced the same distance from the terminal planar faceof its respective arm.

References Cited in the le of this patent UNITED STATES PATENTS 548,899Wade Oct. 29, 1895 1,598,293 Luck Aug. 31, 1926 2,026,061 Prikel Dec.3l, 1935 2,616,370 Foster Nov. 4, 1952 2,633,329 LeBus Mar. 31, 19532,799,224 Long July 16, 1957 2,853,944 Robertson Sept. 30, 1958 FOREIGNPATENTS 701,074 Great Britain Dec. 16, 1953

